In a swash plate type variable capacity compressor in the related art, an inclination angle of a swash plate is changed by controlling the pressure of a crank chamber in the rear of a piston to change a stroke (discharge capacity) of the piston. In detail, when the pressure of the crank chamber is decreased, the inclination angle of the swash plate is increased, and as a result, the discharge capacity of the compressor is increased. In contrast, when the pressure of the crank chamber is increased, the inclination angle of the swash plate is decreased, and as a result, the discharge capacity of the compressor is decreased.
Furthermore, the variable capacity compressor includes a first communication passage that allows a discharge chamber and a crank chamber to communicate with each other, a second communication passage that allows the crank chamber and a suction chamber to communicate with each other, a control valve mounted on the first communication passage, and an orifice mounted on the second communication passage, and a balance between an inflow amount of high-pressure refrigerant gas that flows into the crank chamber through the first communication passage and an outflow amount of refrigerant gas that flows out from the crank chamber through the second communication passage is controlled by controlling an opening level of the first communication passage with the control valve to change the pressure of the crank chamber.
However, in the variable capacity compressor, each unit of the compressor is lubricated by mixing the lubrication oil in the refrigeration gas. As a result, the lubrication oil that flows out from the compressor to the circuit is reduced, that is, an oil circulation rate (OCR) is decreased to enhance system efficiency. Furthermore, the decrease of the OCR in a capacity control region is required in that the OCR is increased (deteriorates) in the capacity control region as compared with a maximum capacity operation.
As a result, in Patent Document 1, a centrifugal oil separator is provided on a discharge passage from the discharge chamber to separate oil and return the separated oil to the crank chamber.
Furthermore, in Patent Document 2, an oil separator (oil separation mechanism) is provided on the first communication passage (a passage of control gas from the discharge chamber to the crank chamber) to separate lubrication oil from the control gas and allow the separated lubrication oil to flow down to the crank chamber.